Kinetics of reaction between hydroxyl radical formed by beta-rays in tritiated water and tea catechin: Application of the solid state spin trapping method

Abstract

The aqueous solutions of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) containing various amount of (-)-epigallocatechin gallate (EGCg) were mixed with tritiated water, then frozen and β-ray irradiatedin situ for 90 days at −80°C. ESR spectra were measured as a function of time after melting the sample at room temperature. The intensity of the hydroxyl (OH)_ radical adduct, DMPO-OH, was obtained by the extrapolation to zero time. The ratio of the reaction rate constants of the OH radical with EGCg and DMPO,kEGCg/kDMPO, was obtained kinetically. The result was compared with the case of DNA and EGCg in tritiated water, in order to make clear the mechanism of the protection of DNA from the radiation-induced scission with EGCg.